U.S. patent number 4,444,262 [Application Number 06/449,079] was granted by the patent office on 1984-04-24 for method of using amines as sacrificial agents for chemical flooding.
This patent grant is currently assigned to Texaco Inc.. Invention is credited to Phillip E. Figdore, Helen K. Haskin.
United States Patent |
4,444,262 |
Haskin , et al. |
April 24, 1984 |
Method of using amines as sacrificial agents for chemical
flooding
Abstract
The disclosed invention is a method of injecting an amine
sacrificial agent into a hydrocarbon formation in conjunction with
a chemical flooding process to reduce the loss of injected
chemicals to the formation by adsorption and precipitation.
Inventors: |
Haskin; Helen K. (Houston,
TX), Figdore; Phillip E. (Bellaire, TX) |
Assignee: |
Texaco Inc. (White Plains,
NY)
|
Family
ID: |
23782784 |
Appl.
No.: |
06/449,079 |
Filed: |
December 13, 1982 |
Current U.S.
Class: |
166/270.2;
166/275; 507/251; 507/936 |
Current CPC
Class: |
C09K
8/86 (20130101); Y10S 507/936 (20130101) |
Current International
Class: |
C09K
8/86 (20060101); C09K 8/60 (20060101); E21B
043/22 () |
Field of
Search: |
;166/273-275
;252/8.55D |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Suchfield; George A.
Attorney, Agent or Firm: Kulason; Robert A. Park; Jack H.
Delhommer; Harold J.
Claims
What is claimed is:
1. A method of recovering petroleum from a subterranean hydrocarbon
formation which is penetrated by at least one injection well and at
least one production well wherein chemicals are injected into the
formation to sweep oil through the formation, which comprises:
injecting into the formation a solution containing about 0.01% to
about 5.0% by weight of an amine sacrificial agent designed to
prevent the loss to the formation of said injected chemicals,
said amine sacrificial agent selected from the group consisting of
ethylenediamine, polyamines and mixtures thereof.
2. The oil recovery method of claim 1 wherein said injected
chemicals are selected from the group consisting of surfactants,
solubilizers, sulfonates and viscosity enhancers.
3. The oil recovery method of claim 1, wherein the sacrificial
agent is injected into the formation in solution with said injected
chemicals.
4. The oil recovery method of claim 1, wherein the sacrificial
agent is injected into the formation prior to the injection of said
injected chemicals.
5. The oil recovery method of claim 1, wherein the average
molecular weight of the polyamine sacrificial agent is about 100 to
about 1000.
6. The oil recovery method of claim 1, wherein about 0.005 to about
0.4 pore volumes of sacrificial agent is injected into the
formation.
Description
FIELD OF THE INVENTION
This invention relates to a method of injecting chemicals into a
petroleum reservoir for the purpose of increasing petroleum
recovery. More particularly, the invention pertains to the use of
ethylenediamine and polyamines as sacrificial agents to decrease
adsorption and precipitation of chemicals such as surfactants and
polymers within petroleum reservoirs.
BACKGROUND OF THE INVENTION
One of the most vexing problems in the use of surfactant flooding
for enhanced oil recovery is the frequent substantial loss of
surfactant and polymer due to adsorption on the formation matrix
and precipitation by polyvalent cations such as calcium and
magnesium. Chemical adsorption on the formation matrix
significantly decreases surfactant flood efficiency, and because it
is necessary to inject a greater quantity of surfactant and
polymer, increases the cost of any surfactant flood.
Additionally, most surfactants are satisfactory for surfactant
flooding only if the calcium and magnesium concentrations of the
formation water fall below about 500 ppm. Petroleum sulfonates, the
most popular type of surfactants, precipitate where divalent ion
concentrations exceed about 500 ppm. Such precipitation renders the
sulfonates inoperative for recovering oil and in some instances,
causes formation plugging.
Many subterranean petroleum-containing formations are known to
exist which contain polyvalent ions such as magnesium and calcium
in concentrations far in excess of 500 ppm. The most common of
these reservoirs are limestone formations which may have polyvalent
ion concentrations from 200 to 20,000 ppm in the original connate
water. Similar polyvalent ion concentrations can also be found in
sandstone reservoirs containing kaolinite and bentonite clays,
which also provide additional problems in adsorption of
surfactant.
Where high divalent ion concentrations exist, most petroleum
sulfonates cannot be used because the high surfactant losses due to
precipitation and adsorption on the matrix render use uneconomical.
In such an environment, the flood water will lack the surfactant
necessary to substantially decrease the interfacial tension between
water and petroleum. Furthermore, precipitated petroleum sulfonate
often plugs small flow channels in subterranean hydrocarbon
formations. Such plugging from precipitated surfactants decreases
formation porosity and injectivity, causing substantial decreases
in oil displacement efficiency.
Nonionic surfactants, such as polyethoxylated alkyl phenols,
polyethoxylated aliphatic alcohols, carboxylic esters, carboxylic
amides and polyoxyethylene fatty acid amides have a somewhat higher
tolerance of polyvalent ions than do the more commonly utilized
anionic surfactants which generally have water soluble sulfonate,
sulfate, phosphate or carboxylate groups. However, while it is
technically feasible to employ a nonionic surfactant solution to
decrease interfacial tension between the injected aqueous
displacing medium and the petroleum contained in hydrocarbon
formations, these surfactants are frequently not economically
feasible for several reasons. First, nonionic surfactants are also
subject to adsorption on the formation matrix, which can
drastically decrease the amount of surfactant available for
lowering interfacial tension. Second, nonionic surfactants are not
as effective on a per unit basis as are the more commonly used
anionic surfactants. Third, nonionic surfactants have a higher cost
per unit weight than do anionic surfactants. Furthermore, nonionic
surfactants are ineffective at formation temperatures above their
cloud points.
Various chemicals have been employed as sacrificial agents to
pretreat formations to decrease the adsorption of subsequently
injected surfactants or to tie up polyvalent cations and prevent
them from precipitating surfactants from the flood medium. Some
examples include the use of aqueous solutions of pyridine as
disclosed in U.S. Pat. No. 3,414,054, the use of sodium carbonate
and inorganic polyphosphates as disclosed in U.S. Pat. No.
3,469,630, the use of metal phosphates as disclosed in U.S. Pat.
No. 3,688,844 and the use of modified lignosulfonates as described
in U.S. Pat. Nos. 4,133,385; 4,142,582 and 4,172,497.
U.S. Pat. No. 4,036,300 discloses the use of
ethylenediaminetetraacetic acid and other aminopolycarboxylic acids
as chelating agents to bind multivalent cations to insure the
stability of a micellar dispersion in surfactant flooding.
SUMMARY OF THE INVENTION
The disclosed invention is a method of injecting amines selected
from the group consisting of ethylenediamine and polyamines, or
mixtures thereof, into a hydrocarbon formation in conjunction with
a chemical flooding process to reduce the loss of injected
chemicals to the formation by adsorption and precipitation. These
sacrificial agents may be injected either in a preflush solution
prior to the injection of surfactant or in solution with injected
chemicals such as surfactants, solubilizers, sulfonates and
viscosity enhancers. The sacrificial agents are preferably injected
in a concentration of about 0.01% to about 5.0% by weight of the
subject amines.
DETAILED DESCRIPTION
In carrying out this invention, a solution containing amines
selected from the group consisting of ethylenediamine and
polyamines is injected as a sacrificial material through an
injection means comprising one or more injection wells into a
hydrocarbon formation. The sacrificial material is injected in a
manner to substantially occupy or cover all potential adsorption
sites of the rock within the hydrocarbon formation, thereby
reducing the extent of injected chemical adsorption. The phrase
"adsorption sites of the formation rock" is used to mean those
portions of the formation rock surface, including matrix pores,
which are capable of adsorbing a chemical compound from a solution
on contact. It is also believed that the sacrificial material of
the present invention reacts with polyvalent cations such as
calcium and magnesium to prevent them from reacting with
surfactants and other chemicals injected into the formation.
The sacrificial agents of the present invention are amines selected
from the group consisting of ethylenediamine and polyamines.
Polyamines are defined as linear, branched or cyclic polymers of
the formula --CH.sub.2 CH.sub.2 N--; or linear, branched and cyclic
copolymers thereof. It is preferred that the polyamines have an
average molecular weight of about 100 to about 1000. An especially
preferred polyamine is Polyamine PA-400, a trademarked product sold
by Texaco Chemical Co.
It is most desirable that a sacrificial material be less expensive
than the surfactant employed and be readily adsorbed by the rock in
the hydrocarbon formation. The presence of the adsorbed sacrificial
material should also retard or eliminate the subsequent adsorption
of surfactant on the adsorption sites of the formation rock. A lack
of sacrificial agent interaction with other injected chemicals is
also advantageous. Such guidelines are, however, flexible. It is
possible that a sacrificial agent may be a highly desirable
material to use even though it may cost considerably more than a
surfactant, if it can be used in substantially smaller
concentrations than the surfactant.
The highly undesirable loss of surfactant in chemical flooding may
generally be attributed to two phenomena. The first phenomenon is
chemical removal or inactivation of the surfactant after contact
with polyvalent cations or other materials dissolved in the
formation fluids. The second phenomenon is adsorption within the
formation due to physical contact of the surfactant with the
formation matrix. It is believed that both phenomena exist
simultaneously to varying degrees in most chemical flooding
operations.
It is believed that sacrificial agents generally work by one or
more of several chemical mechanisms. However, it must be emphasized
that these chemical mechanisms are theoretical and the extent to
which any one of these mechanisms may be responsible for the
effectiveness of a sacrificial agent is not known. One possible
chemical mechanism is the complexing of the sacrificial agent with
polyvalent cations in solution, both by neutral and by charged
sacrificial complexing agents. To the extent that the sacrificial
agent complexes with the polyvalent cations in solution, there will
be less polyvalent cations left for the surfactant to interact
with.
A second possible mechanism is the electrostatic attraction of the
matrix and the sacrificial agent for each other. This is
predominantly controlled by the surface charge of the matrix which
is mainly determined by the pH of the formation water or by other
potential determining ions. The formation brine is a secondary
controlling factor since it can screen some of the surface charge
from the suractant, allowing it to approach the surface more
closely and thus more readily absorb. This is known as a double
layer effect.
A third type of mechanism is believed to be hydrogen bonding of
polar and organic sacrificial materials to uncharged portions of a
clay matrix. A fourth possible mechanism arises from the fact that
polymers have many functional groups and may attach themselves to
the rock surface in many places, thereby blocking the sites on
which injected chemicals could absorb. In this manner, the large
size of polymer molecules may block entrances to very small pores
where much of the surface area and adsorption sites lie.
Furthermore, the character of the formation matrix, be it
carbonate, bentonite, kaolinite or something between these three
disparate types of substrates also has a significant impact upon
the effectiveness of the sacrificial material. The surfactant
itself that is employed also alters adsorption, but it is generally
not as critical as the type of formation matrix.
The amine sacrificial agents of the present invention are effective
in reducing the adsorption of any type of surfactant used for
enhanced oil recovery on many substrates under a wide range of
brine and temperature conditions. This contrasts to the cited
references in which the substrates used are usually limited to
Berea sandstone at a given temperature and a given brine. The
sacrificial material should be injected into the subterranean
formation either in a slug preceding the injected chemicals or in
solution along with the surfactant, solubilizer or viscosity
enhancing chemicals. The use of the sacrificial material of the
invention substantially dcreases chemical loss, most particularly
surfactant loss thereby allowing the surfactant to achieve the
desired lower interfacial tension, which increases oil
recovery.
Both the sacrificial material and the surfactant may be injected
into the subterranean hydrocarbon formation in an aqueous solution
or in a non-aqueous solution with a hydrocarbon solvent, depending
upon other requirements. However, economic considerations usually
require that the materials be injected in aqueous solutions
whenever possible.
The quantity of sacrificial amine to be injected should be
sufficient to occupy substantially all of the active adsorption
sites of the formation matrix, in order to effect the maximum
reduction in the amount of surfactant loss to the formation. If
less than this optimum amount is used, which will, of course, vary
from formation to formation, the corresponding reduction in
surfactant loss to the formation will not be as great as in the
case where the formation adsorption sites were completely
saturated. Similarly, if more than the amount of amine necessary to
occupy all of the active adsorptions sites and polyvalent cations
is injected into the hydrocarbon formation, no additional reduction
in oil displacement efficiency will result. However, the use of
excess sacrificial materials will substantially increase the cost
of the chemical flooding. The preferred total amount of sacrificial
amine injected will vary with the composition of the formation, the
thickness of the formation, the pattern area to be swept and
various other formation characteristics.
The concentration of amine of the present invention injected does
not appear to be critical, since it is the total amount of
sacrificial material injected that normally determines the
effectiveness in preventing surfactant loss. It is preferred that
the amine of the present invention be injected in a solution with a
concentration ranging from about 0.01% to about 0.5% by weight. It
is further preferred that about 0.005 to about 0.4 pore volumes of
sacrificial material solution should be injected into the
formation, as required to match the chemical slug size.
Since the adsorptivity of reservoirs varies considerably depending
on the type of formation encountered and the polyvalent ion
complexing substantially depends upon the concentration of cations
present, considerable knowledge of the formation is necessary in
order to determine the optimum amount of amines of the present
invention to be injected in order to achieve the maximum reduction
in surfactant loss. If the hydrocarbon formation is a relatively
clean sandstone lacking substantial clay content, significantly
smaller quantities of sacrificial agent will be needed than in the
case where the formation contains large amounts of highly adsorbant
clays such as bentonite.
The effectiveness of using ethylenediamine or polyamines for
reducing surfactant, solubilizer and polymer loss in chemical
flooding operations is demonstrated by the following examples.
These examples are presented for illustrative purposes and should
not be construed to limit the scope of the invention, which is
defined in the claims which follow.
EXAMPLES
The surfactant loss from a stock petroleum sulfonate/solubilizer
system was measured under varying conditions both with and without
the test sacrificial agent. All agents were tested in two different
brines at 43.degree. C. and 74.degree. C. with three different
substrates: bentonite, kaolinite and calcium carbonate. Brine #1
was a soft brine with a total dissolved solid (TDS) content of
about 96,500 ppm and a divalent ion concentration of 548 ppm. Brine
#2 had a total dissolved solids content of 94,340 ppm and a
divalent ion concentration of 9,190 ppm. All solutions were tested
to determine the actual petroleum sulfonate concentration present
prior to the beginning of testing. The percent change in surfactant
loss for each agent is listed in Table I.
The brines employed in the examples contained the following
materials:
______________________________________ Brine #1 Brine #2
______________________________________ Ca 425 ppm 7120 ppm Mg 123
2066 Na 37,225 25,863 HCO.sub.3 512 708 SO.sub.4 0 1763 Cl 58,217
56,815 TDS 96,502 94,335 Ionic 3.3 3.3 Strength
______________________________________
The petroleum sulfonate/solubilizer stock was prepared as a 2.6%
solution containing 0.53% of a petroleum sulfonate sold under the
trademark of Witco TRS-18 by Witco Chemical Co., 1.23% of a
petroleum sulfonate sold under the trademark Witco TRS-40 by Witco
Chemical Co. and 0.8% of an ethoxylated anionic surfactant sold
under the trademark N-60CS by Texaco Chemical Co.
The sacrificial agents tested were ethylenediamine and Polyamine
PA-400. Lignosite 458 and Uni-Cal Domestic are two commercially
available trademarked lignosulfonates sold by Georgia Pacific Inc.
and Union Oil of California, respectively. The lignosulfonates were
tested for comparative purposes only.
All tests run with bentonite clay substrates were conducted with 40
ml of petroleum sulfonate/solubilizer stock with and without the
sacrificial agent to be tested and 2 grams of bentonite. The other
substrates were tested similarly: for kaolinite, 10 grams of
substrate and 40 ml of petroleum sulfonate/solubilizer were used;
for calcium carbonate, 20 grams of substrate and 50 ml of petroleum
sulfonate/solubilizer were used.
Dry substrate chosen from the group of bentonite clay, kaolinite
clay and calcium carbonate was weighed into bottles and the
petroleum sulfonate/solubilizer and sacrificial agent mixtures were
added by pipet. The bottles were tightly capped and then gently
agitated in a preheated oven at 43.degree. C. or 74.degree. C.
After 24 hours, the bottles were removed and centifuged before the
liquid was decanted for analysis.
A 2-phase titration was employed to determine the concentration of
petroleum sulfonates and solubilizers present in the liquid. The
difference between the petroleum sulfonate/solubilizer
concentration after testing and the original concentration reflects
the loss of petroleum sulfonate/solubilizer to the substrate and
brine environment. Surfactant losses with and without the test
sacrificial agent were compared to yield the percentage changes in
surfactant loss shown in Table I. By use of the different
substrates and the varying divalent ion concentrations, surfactant
loss due to adsorption and precipitation was measured.
An examination of Table I indicates that the ethylenediamine and
polyamine had similar effects in all three substrate environments
and superior chemical loss prevention effects over the commercially
available lignosulfonates in a bentonite environment. Thus, in a
predominantly swelling clay formation, ethylenediamine and
polyamines would be the sacrificial agents of choice.
Many other variations and modifications may be made in the concept
described above by those skilled in the art without departing from
the concept of the present invention. Accordingly, it should be
clearly understood that the concepts disclosed in the description
are illustrative only and are not intended as limitations on the
scope of the invention.
TABLE I
__________________________________________________________________________
PERCENT CHANGE IN SURFACTANT LOSS.sup.a Brine #1.sup.c Brine
#2.sup.d Bentonite Kaolinite CaCO.sub.3 Bentonite Kaolinite
CaCO.sub.3
__________________________________________________________________________
Tested at 43.degree. C. Ethylenediamine (2.5%) -25 0 0 -65 +90 +10
Polyamine PA-400 (2.5%) -90 -15 +15 -50 +140 +25 Lignosite 458
(2.5%) -35 0 -50 -40 +40 -20 Uni-Cal Domestic (2.5%) -30 +30 -85
-25 +15 -25 Tested at 74.degree. C. Ethylenediamine (2.5%) -95 -10
0 -60 +90 0 Polyamine PA-400 (2.5%) -90 -10 -10 -50 +90 0 Lignosite
458 (2.5%) -60 0 -40 -30 +25 -40 Uni-Cal Domestic (2.5%) -20 -25
-65 -15 -10 -55
__________________________________________________________________________
.sup.a To nearest 5%, less than 10% reported as zero. .sup.b
Sacrificial agent concentration in parentheses as weight percent.
.sup.c Total dissolved solids = 96,500 ppm, Ca.sup.+2 + Mg.sup.+2 =
548 ppm. .sup.d Total dissolved solids = 94,340 ppm, Ca.sup.+2 +
Mg.sup.+2 = 9190 ppm.
* * * * *